I would go with Aura sphere over focus blast because of the accuracy issue...and then Psychic for stab and then two other moves to cover as many types as possible... e.g Ice beam/thunderbolt.

An idea which I haven't tried out is a defensive Mewtwo as it can learn barrier, amnesia and recover to make it indestructable...although status would be a problem. Also with only one offensive move Psychic or Aura sphere may not be good due to dark and ghost types immunity so maybe it'd have to be ice beam...just an idea

One of the best special sweepers in the game right here. Mewtwo can Calm Mind up and Taunt away any other attempts to set up, phaze, psych up, status, or otherwise interfere with its setup with its massive speed. Taunt's new duration of two to four turns makes a Recoverless Mewtwo better than it used to be, as you are no longer forced to Taunt every other move. Ice Beam and Shadow Ball hit the vast majority of the uber metagame, but you'll need either Ice Beam or Aura Sphere in order to hit Blissey. Mewtwo is one of those Pokémon that badly wants five or six move slots.

Physical Mewtwo is no joke. Ice Punch hits ubers on their weak physical defense, Earthquake covers stuff like Metagross and Dialga; Fire Blast does a lot more damage to Groudon. If you fear Ho-oh use Stone Edge in the last slot, otherwise pick a move that feels appropriate and run with it. It's a shame Shadow Ball is special now and Mewtwo doesn't get a physical ghost move like Shadow Claw to make up for it.

The given EVs outrun speed-boosting Lugia and other base 110 speed Pokémon. Don't bother trying to outspeed Darkrai, whose existence means physical Mewtwo isn't nearly as effective as it used to be: if you EV Mewtwo to outspeed Darkrai, Brick Break can't even OHKO it if Darkrai invests a mere 8 EVs into HP. You can defeat it with an Expert Belt (put Brick Break over Earthquake), but you'll have to sacrifice some attack power to do so. It's not a bad idea though; use 216 speed EVs with Jolly if you want to try that.

Fighting's super effective against normal, rock, ice and dark so it is a handy type to haveFocus punch is also physical and Mewtwo is better at special but if you want a mixed sweeper then maybe I guess...but anyway yeah it's a bit of a "lucky move" in most cases when you don't have spore, a paralysing move or substitute in use.